Dimethoxy-3-isochromanone

Information about the electronic structure of the 4,5-dimethoxy-o-quinodimethane adduct 46 in the solid state, prepared from 6,7-dimethoxy-3-isochromanone 42 (Rj = R4 = H R2 = R3 = OMe), comes from ESCA measurements [43]. In accord with the crystal structure analysis [43, 58], this cycloadduct, which contains the electron-rich dimethoxyphenyl moiety, shows an intermolecular donor-acceptor interaction, in particular, of the methoxy oxygen to the unit. 

Coned. HCl added rapidly at 80° to a stirred soln. of 3,4-dimethoxyphenylacetic acid and acetic acid, then 37%-formalin added immediately, stirred and heated 1 hr. on a steam bath 6,7-dimethoxy-3-isochromanone. Y 56-85%. F. e. s. J. Finkelstein and A. Brossi, Org. Synth. 55, 45 (1976). 

Isochroman-3-ones.2-(3,4-Dimethoxyphenylacetyl)-4,5-dimethoxyphenylacetic acid heated 0.5 hr. at 190° in decalin l-(3,4-dimethoxybenzylidene)-6,7-dimethoxy-3-isochromanone. Y 80%. I. W. Elliott, J. Heterocyclic Chem. 7, 1229 (1970). 

In connection with the anodic intramolecular coupling of 1-benzyltetrahydroiso-quinoline derivatives, the anodic oxidation of 4-(3,4-dimethoxybenzyl)-6,7-dimethoxy-isochromanone 15 has been studied rather extensively. The main product obtained from the isochromanone is a y-lactone, 7a,8-dihydro-3,10,ll-trimethoxy-2 H-phenanthro[9.8a, b]furan-2,7(5 H)-dione 16 13 ... 

Isochromanones on condensation with p-phenylethyl amines, followed by Bischler-Napieralski cyclisation and NaBH reduction furnish berbine alkaloids in good to excellent yields. The 7,8-dimethoxy and mcthylenedioxy isochromanones prepared by lithiation methods provide the 9,10-oxygenated berbine alkaloids, such as tetra-hydropalmatine 51a canadine stylopine 57c , sinactine... 

Ion-exchange resins, 55, 3 Iron, tricarbonyldiene complex, 57, 16 Iron pentaearbonyl, 57, 108 58, 61 Isobutyl fluoride, 57, 73 3-ISOCHROMANONE,6,7-DIMETHOXY-, 55,45... 

Conversion of pyrans into pyridines is well established, but an example of the converse reaction was recently described in which the benzylisoquinoline (181 R = 6,7-dimethoxy) was treated with cyanogen bromide to give the iso-chroman (182). Oxidation of alpinigenine (183), which is present in several species of poppies, gave the isochromanone (184). ... 

Pyrolysis of isochromanones in the gas phase at 500 °C, with resultant loss of carbon dioxide, has afforded a new synthesis of 4,5-dimethoxy-, 4,5-methylenedioxy-, and 4-methoxy-benzocyclobutene. Photosolvolysis of 2-(3,5-dimethoxyphenyl)ethyl methanesulphonate in 50% aqueous methanol gave inter alia small amounts of 3,5-dimethoxybenzocyclobutene. 

A related synthetic approach to yohimbine synthesis was utilized by Pandey and his coworkers (Scheme 3.91) (141,142). Thus, isochromanone 518 was converted to bromoester 519 which was then condensed with tryptamine to afford tetracyclic amide 520. Alternatively, 520 could be prepared by treatment of 518 with ammonia to provide 521 which was then AT-tryptophylated. Cyclization of 520 under standard conditions provided the dimethoxy-yohimbane derivative 522. 

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